Method and apparatus for power transmission and actuation



June 21, 1966 J. E. LINDBERG, JR 3,

METHOD AND APPARATUS FOR POWER TRANSMISSION AND ACTUATION Original FiledSept. 30, 1960 Sheets-Sheet 1 33 5/ 3 f sa 2;

2 4 ACTUIATED FIG. I

5-0 DEVICE 7 .52 2 A ra/ rio (58 62 3' 9, l u N FIG-3 INVENTOR. Jfl/l AU/VOBF 196 WM a.

June 21, 1966 J. E LINDBERG, JR 3,256,686

METHOD AND APPARATUS FOR POWER TRANSMISSION AND ACTUATION Original FiledSept. 30. 1960 5 Sheets-Sheet 2 Pic. 6

Z INDUCTIVE HEATING ELEMENT 0 Z RADIO FREQUENCY FIG. 7

200 F16. IO

INVENTOR. Ja /v A/A/DBE/P BY @m@% June 21, 1966 J. E. LINDBERG, JR

METHOD AND APPARATUS FOR POWER TRANSMISSION AND ACTUATION 5 Sheets-Sheet3 Original Filed Sept. 30, 1960 INVENTOR. JO/I/V E ZM/DBl-WG June 21,1966 METHOD AND APPARATUS FOR POWER TRANSMISSION AND ACTUATION J. E.LINDBERG, JR

Original Filed Sept. 50, 1960 emf.

O 9 o y r 5 Sheets-Sheet 5 INVENTOR. JOHN E. LINDBEPG ATTORNEY UnitedStates Patent 3,256,686 METHOD AND APPARATUS FOR POWER TRANS- MISSIONAND ACTUATION John E. Lindherg, Jr., 1211 Upper Happy Valley Road,Lafayette, Calif.

Original application June 3, 1964, Ser. No. 372,248, which is a divisionof Ser. No. 60,250, filed Sept. 30, 1960. Divided and this applicationApr. 27, 1965, Ser. No. 461,220

9 Claims. (Cl. 6025) This application is a division of applicationSerial Number 372,248, filed June 3, 1964, which was a division ofapplication Serial Number 60,250, filed September 30, 1960, nowabandoned, which was a continuation-inpart'of application Serial Number759,717, filed Septemher 8, 1958, now abandoned.

This invention relates to improvements in method and apparatus for powertransmission and actuation. It can be used to actuate any device capableof applying mechanical force, including hydraulic systems, gas turbines,loudspeakers, valve actuators, and the like.

Conventional power transmission and actuator systems are generally bulkyand excessively heavy. They are complex units, expensive to overhaul andrepair. The operation of many of them depends upon liquids or gases thateither have to be contained in rather large reservoirs to providepotential energy or have to be circulated by pumps. In addition, manysystems require close-fitting leak-proof seals which are subject tofailure at elevated temperatures. Often, special fittings, valves, andtransmission lines are required as integral parts of the actuator unit.

Adequate power transmission systems are vital on modern aircraft, wherethey are used for retracting and lowering the landing gear, flapcontrol, afterburner control and many other things. But the actuatorsystems heretofore available have proved inadequate in the hightemperature environment experienced by high-speed aircraft and by guidedmissiles. Consequently, major aircraft companies have been trying todevelop 3000-p.s.i. actuator systems able to operate between 65 F. and1000 F. Much current research is directed toward development ofhydraulic systems capable of operating in these environments, butperformance data on hydraulic pumps indicate that, as yet, no dependablepump has been developed which will function properly over the full -65F. to 1000 F. range. Even if there were such pumps, contemporaryhydraulic fluids are, at best, able to perform satisfactorily onlywithin the range of 100 F. to 700 F., while the seals that are necessaryin a hydraulic system have a relatively short life at 700 F. 4

Moreover, hydraulic systems have many disadvantages, even if able tofunction properly. A pump external to the actuating system is necessary,as are hydraulic accumulators in some cases; high pressure fittings,control valves, and transmission lines must be installed as an integralpart of the system and these result in excessive bulk and weight. Thefluids involved often constitute a fire hazard, and the system must beprimed before operation. In addition, when replacing a defective unitbecause of a breakdown, other parts of the system are often affected,resulting in expensive procedures.

One object of this invention is to provide an actuator (i.e.,power-transmission) system capable of satisfactory operation at both (1)elevated temperatures in the range of 1000 F. and higher and at highpressures and (2) low temperatures (e.g. 65 F.) and at low pressures.Another object is to provide an actuator that does not depend uponliquids of any kind. It achieves these objects by utilizing certainthermodynamic properties of special classes of materials to alter theinternal pressure 3,256,6dfi

Patented June 21, 1966 with the temperature of the materials.

The actuating systems of this invention are simpler, more compact, andmore economical to operate than conventional systems, and do not dependupon external pumps or reservolrs.

A further aim of this invention is to provide actuating systemsrequiring no valves, fittings, or fluid or vapor transmission lines, asdo numerous present-day actuators, and requiring no priming operations.

Over and above eliminating many disadvantages of conventional actuatingsystems, as well as solving the problem of elevated temperature andpressure actuation, this invention presents a much smaller fire hazardthan other contemporary systems, and will function with any source orsink of heat.

Other objects and advantages of the invention will appear from thefollowing detailed description of some preferred embodiments thereof.

In the drawings:

FIG. 1 is a view in side elevation and in section of an actuatorembodying the principles of this invention and incorporating asingle-unit bellows-diaphragm type of actuating device for control bytemperature variation. The actuator is shown in its contracted position,and an accompanying electrical circuit is indicated diagrammatically.

FIG. 2 is a view like FIG. 1 of the same actuator in its expandedposition.

FIG. 3 is a view like FIGS. 1 and 2, showing a dualunit reciprocatingactuator embodying the principles of the present invention.

FIG. 4 is a view like FIG. 1 of a modified form of a single-unitreciprocating actuator of this invention, shown in its contractedposition.

FIG. 5 is a view like FIG. 4, showing the same actuator in its extendedposition.

FIG. 6 is a view in elevation and partly in section of a windshieldwiper powered by a dual-unit actuator like that of FIG. 3.

FIG. 7 is a fragmentary and generally schematic view of a part of anactuator like those of FIGS. l6, but provided with analternating-current type of electrical heater.

FIG. 8 is a View like FIG. 7 showing a radio-frequency type ofelectrical heater.

FIG. 9 is a view like FIG. 7 showing an actuator heated by a flame.

FIG. 10 is a view like FIG. 7 of an actuator utilizing solar heat.

FIG. 11 is a view in side elevation and in section of a modified form ofactuator of this invention, incorporating a single unit cantileverbellows. The bellows is shown in its contracted position with anelectrical heater indicated diagrammatically.

FIG. 12 is a view like FIG. 11, but shows the bellows in its extendedposition.

FIG. 13 is a view in side elevation and in section of a cantilever typeof actuating device employed as a shock absorber and gas spring, withcontrol by the variation in voltage of an electrical heater. The bellowsis shown in its contracted position.

FIG. 14 is a view like FIG. 13 but showing the bellows in its extendedposition.

FIG. 15 is a fragmentary enlarged view showing a modification of thecontact elements of FIGS. 13 and 14, the contacts being shown in theiropen position.

' FIG. 16 is a view like FIG. 15, showing the contacts in their closedposition.

FIG. 18 is a view in side elevation and in section of a flow-regulatingdevice incorporating an actuator of this invention.

FIG. 19 is a diagrammatic view in side elevation and in section of apiston-cylinder type of actuator, embodying the principles of thisinvention.

FIG. 20 is a diagram of an electrical wave form (current or voltageplotted against time) that may be used in the actuator of FIG. 19.

FIG. 21 is a view in elevation and in partial section of a heatingcapsule and some adjacent parts.

FIG. 22 is a view in elevation and in partial section of a modified formof heating unit.

FIG. 23 is a view in elevation of another modified apparatus for heatingthe gas transfer agent.

FIG. 24 is a diagrammatic view in elevation and in section of anarc-discharge heating capsule.

GENERAL PRINCIPLES OF THE INVENTION Metallic hydrides are capable ofingassing (taking in gas in either a chemical or physical action) ordegassing (also called outgassing), upon the application or removal ofheat. For example, certain classes of hydrides release large amounts ofhydrogen solely as a result of the application of heat, while otherhydrides absorb hydrogen solely because of the application of heat.Although this phenomenon has been observed for many years, about theonly application of it, heretofore, has been in the electronic tubeindustry, where getters take up the residual gases remaining in thetubes after the tubes have been sealed. However, as will be seen, theseingassing or outgassing substances, hereafter termed as gas-transferagents, represent, under the right conditions, a very useful means forstoring energy. Moreover, this energy may be converted to perform usefulwork whenever desired by varying the temperature or pressure conditions.

One way of utilizing this phenomenon is to enclose a gas-transfer agentof this invention in a container of variable dimensions, so constructedthat the dimensions always conform to equilibrium conditions, i.e., to abalance of the internal forces against the external forces. Theapplication of heat to such an enclosed gas-transfer agent then resultsin the alteration of the internal pressure Within the container due tothe emission of the gas from the gas-transfer agent, with theconsequence that the container dimensions alter in order to maintainequilibrium. This dimensional alteration is accomplished by movement ofsome part of the container, and this movement can be used to actuate orcause. movement of another device which will perform useful Work.

A few devices of variable dimensions suitable for my invention will bediscussed in detail below. Before considering them, however, it isdesirable toenquire into the general properties of the gas-transferagents suitable for this invention.

GAS SORPTION There are at least three mechanisms by which gases orvapors may be taken up by a solid. (1) The solid may chemically reactwith the gas or vapor. (2) The solid may physically adsorb the gas; thenthe gas condenses as a layer on the surface of the solid. (3) The solidmay physically absorb the gas; then gas enters into the interior of thesolid in much the same manner as gas dissolving in a liquid. In manycases, the solid may take up gas by both adsorption and absorption, andin many cases it is difficult to determine the exact nature of themechanisms involved; so the generic term sorption and its derivativessorptive, sorbent, etc., are used to include both or either ofabsorption and adsorption. Materials differ widely with respect to theircapacity for sorption or desorption. Some reactions are irreversible;that is, once a gas or vapor is sorbed (or deso'rbed) by some solidsunder the initiating circumstances, it cannot be desorbed (or re-sorbed)except under the most extreme treatment; with certain other classes ofsubstances, sorption and desorption of a gas or vapor is reversible andcan be made to occur repetitively for an unlimited number of cycles.

For every sorptive condition of a mixture of a gas or vapor and asorbent substance, at any one temperature, there is a certain presure atwhich this mixture will be in thermodynamic equilibrium. When the gas orvapor (sometimes both) is a thermodynamic phase of the sorbentsubstance, this pressure is often called the equilibrium pressure"; whenthe gas is not necessarily native to the sorbing substance, thispressure is often called the dissociation pressure; however, I shall usethe terms interchangeably. It is generally true that under equilibriumconditions a change in any one thermodynamic variable causes a change inthe others. Thus, the 4 equilibrium pressure may be varied by changingthe temperature.

When a gas or vapor is sorbed or goes into solution in the occludingsubstance, heat is evolved or absorbed in the reaction, the reactionbeing termed exothermic if heat is evolved and endothermic if heat isabsorbed. The heat evolved or absorbed is termed the heat of solution.In an exothermic reaction, the sorbing substance may be made to give upits gas when heat is added. In an endothermic reaction, the sorbingsubstance may be made to occlude gas when heated.

SORPTION OF HYDROGEN BY METALS The phenomenon of sorption of hydrogen bymetals merits special consideration because, as will be explained below,many metallic hydrides contain a vast quantity of hydrogen, so thatgreat energy is available. Furthermore, hydrogen is the most mobile ofgases, so that it moves quickly to actuate quickly. The action isreversible for indefinite recycling, is rapid in both directions, andcan be obtained over a wide range of temperatures by proper selection ofthe metal .to be used. The sorption may be adsorption, absorption, ordiffusion into the metal. In general, finely powdered metals take upgases to a much greater extent than solid forms of the metal, because amuch greater surface area is available for interaction. For example,Table I shows an isobar for the adsorption of hydrogen by nickel powder.

Tab/e I.A dsorption of hydrogen on nickel powder [At a pressure of 600mm. of mercury] Solubility in cubic centimeters of Temperature in 0.:gas per grams of nickel Paralleling the phenomenon of physical sorption,there are numerous cases in which hydrogen reacts with metals to formcompounds or solutions of the gas in the solid or liquid metal. Thereare several different types of interaction between hydrogen and theelements: With the elements 'of the main groups IV through VII of theperiodic chart, covalent hydrides are formed such as hydrogen sulfide,arsenic hydride, and silicon hydride. In addition, complex hydrides arealso formed by boron and one or more elements chosen from the groupconsisting of the main groups IV through VII of the periodic chart. Theborohydrides (whose general formula is M (BH where M is a metal and xand y are valence integers) are relatively stable liquids and solids.They are characterized by relativelysmall densities and wide variationin ranges of heats of formation.

With the alkali and alkaline earth metals, i.e., groups I-a and II-a ofthe periodic table, hydrogen forms stoichiometric compounds such assodium hydride and calcium hydride. These are ionic in behavior, withhydrogen as 5. the negative ion. The reactions are reversible andexothermic and are especially useful in this invention.

Hydrogen reacts with aluminum to form aluminum hydride and complexalumino hydrides such as lithium alumino hydride, magnesium aluminohydride, and sodium alumino hydride.

With the elements of groups I-b, lI-b, VI-a, VII-a, and VIII-a (exceptpalladium), hydrogen forms true solutions as indicated by (a) theobservation that the solubility varies as the square root of thepressure and (b) the increase in solubility with increase intemperature. Metals of these groups are designated as Group A metals.Table II gives representative solubility of hydrogen in some Group Ametals.

Table H.Solubility (em /100 g.) of hydrogen at 1 atmosphere pressure intypical metals of Group A Vg=cc. of hydrogen per cc. of hydride at 800C.

Table IH.Sorpti0n of hydrogen by typical metals 0] Group B [In 0111.(S.T.P.) per gram, at 1 atn1.]

T, C Ti V Zr Th Vg=cc. of 11 per cc. hydride at C. d=deusity of themetal.

Although the reactions in both Group A and Group B are perfectlyreversible, a very desirable property in itself, the solubilities ofhydrogen in Group B metals are about 1,000 to 10,000 times those ofhydrogen in Group A metals, as may be seen from Tables 11 and III. Thesolubility in both groups varies with the square root of the pressure,but in Group B the solubility decreases with rise in temperature and thereaction is exothermic, While in Group A the solubility increases withrise in temperature and the reaction is endothermic. Thus, if a sampleof titanium hydride, which has been fully ingassed at room temperature,is heated at one atmosphere pressure to 1000" C., an amount of hydrogenequivalent to 341 cc. of hydrogen per gram of hydride at standardtemperature and pressure will be given up by the sample. Theoreticalrelationships for the solubility of hydrogen as a function of pressureand temperature, derived by the methods of statistical mechanics, havebeen deduced by Fowler and Smithells.

For metals of Group A, the solubility S is given by the equation,

(Equation 1) Where S=solubility reckoned at standard temperature andpressure, :pressure in atmospheres, Q=heat of solution in calories permole of H T=temperature in degrees Kelvin, d=density of the metal.

For metals of Group B:

The values of Q to be used for metals of Group B may be found from TableIV. The calculated values of S are found to be about plus or minus 10%those observed; that is, the values listed in Tables II and III.

Table IV Metal: Q cal/mole H Til0,000 for T 600 C. use 15,000.Zr--17,500 Th22,500 for T 800 C. use 18,600. V-7,700 for T 350 C. use9,100.

SPECIAL ADVANTAGES OF METALLIC HYDRIDES While other solids abs-orb gasesand while there are other ways of obtaining pressure increases withtemperatures, metallic hydrides possess some important specialadvantages. The vaporization of liquids and the pressure increases ofgases due to temperature increases have been used in actuators, but theyrequire special treatments and have many known disadvantages, some ofwhich already have been commented on. As to the other solids, they tendto be restricted in usefulness, low in power output, slow to act, andtend to lose their ability to perform repeatedly.

The metallic hydrides are very quick to respondone actuator I have builthas actuated and de-actuated at sixty cycles per second. Many hydridescontain vast volumes of hydrogen-some have over 1700 times the volume ofthe metal hydride. The reaction is not only reversible; it is capable ofindefinite recycling, thousands or hundreds of thousands of times. Thehydrides can be used to actuate at very high temperatures, and in anenvironment where the pressure is very high, where, again, conventionalactuators are useless.

GENERAL APPLICATION OF GAS-TRANSFER AGENTS TO THE PROBLEM OF AC-TUATIONMy invention provides means for altering the internal pressure of anyclosed container. If the container has dimensions which are variablewith internal pressure, then the resultant change of volume due tochange in internal pressure can be utilized to activate a suitabledevice. The container of variable dimensions used in this manner thusbecomes an actuator.

There are, as previously explained, many hydrides, and their equilibriumgas or-vapor content varies with temperature and pressure. In general,the equilibrium pres sure and temperature have a one-to-onecorrespondence. Hence, by inserting an ingassed or degassed gas-transferagent within a closed container, the internal pressure of the unit maybe varied by the simple expedient of heating or cooling the gas-transferagent.

where d is the density of unsaturated gas-transfer agent, in grams percc.

P is the initial pressure of the loading chamber in atmospheres T is theinitial temperature of the loading chamber, in

Kelvin P is the final pressure of the loading chamber, in atmospheres Tis the final temperature of the loading chamber, in

Kelvin AS is the change in gas or vapor content of the gastransferagent, in cc., when pressure and temperature are varied from P T to P,T

V is the initial volume, in cc., of the loading chamber at pressure Pand temperature T V is the volume, in cc., of the gas-transfer agent inthe loading chamber V is the volume, in cc., of the loading chamber atpressure P and temperature T AV is VV which is the change in volume ofthe loading chamber, in cc.

It is understood that initially the gas-transfer agent in the loadingchamber is surrounded by, and is in equilibrium with, either an inertgas or vapor, or with a gas or vapor of the same chemical composition asthat contained in, or to be released by, the gas-transfer agent. Helium,argon, xenon, and neon are typical suitable inert gases.

The hydrides of Group B are highly superior gas-transfer agents, sincetheir solubilities are rather large, and the reactions are reversible,which means that volume changes can be effected by varying the pressureand temperature in either direction. The equation for the solubility ofhydrogen in metals of Group B has been given above; the reaction isexothermic. From the previously given-Equation 2, the following equationfor AS may be obtained:

(Equation 4) where P and T are in the same units as in theloadingchamber equation.

Several values of AV based on the hydrides of Group B calculated fromthe preceding equations for a series of temperatures and pressures arelisted in Table V for a few hydrides.

Table V Hydride Po, atm. To, 07 P, atm. T, C V

1 5. 1 200 37.2 Vii-0.7 V0. 1 20 204 600 1.11 Vh0.98 V0. 1 20 204 1, 00038 Vh-(LQS V0. 1 20 2, 500 2, 000 6.9 Vii-V0 10 100 204 1, 000 10.4Viv-0.8 V0

50 200 204 1, 000 37.5 Vh0.34 V0. 1 10 0 0.89 Vii-0.88 Vn.

It can be seen from Table V that large pressures are capable of beingdeveloped in a chamber at elevated temperatures. This statement has beenverified by me in my laboratories where I observed that upon heating2.37 grams of zirconium hydride enclosed in a volume of 5 cm. with aninitial pressure of 1 atm., an internal pressure of 1200 p.s.i.g. wasdeveloped. Some of these regions of pressure and temperatures are wellabove those required for aircraft actuation.

One of the unique features possessed by my invention is the fact thatthe rate of ingassing of many hydrides is enhanced by increasing theinitial equilibrium pressure P surrounding the hydride. In fact, therate of ingassing increases linearly with pressure over a very widerange. The usefulness of this phenomenon lies in the fact that cyclicrates of ingassing and degassing may be varied effectively by varyingthe initial internal equilibrium pressure. One of the inert gases,previously referred to, may be chosen to perform this function. Theinert gases possess an important advantage over hydrogen in that, withmany materials, the difiusion rate of the inert gases is negligiblysmall in comparison with hydrogen. This means that, in a hydrideemployed as a gas-transfer agent within the loading chamber, thereplacement of some of the hydrogen with an inert gas within the chamberwill reduce effectively the chance of loss of hydrogen by diffusionthrough the material. Application of this fact may be made to, severalof the applications of my invention which will shortly be discussed indetail.

THE SINGLE-UNIT ACTUATOR 30 OF FIGS. 1 AND 2 An actuator 30 of variabledimensions suitable for application of my invention is depictedschematically in FIGS. 1 and 2. This actuator 30 utilizes a special typeof diaphragm 31, namely, a long-stroke, deep-convolution, constant-areadiaphragm which is free positioning, with complete relaxation within itsstroke and very responsive to small pressure changes. A suitable suchdiaphragm is sold under the trademark Bellofram by the BelloframCorporation, Burlington, Massachusetts. The Bellofram disphragm 31comprises elastomeric material in which high-tenacity pressure-cords ofsuitable fabric are embedded.

In FIG. 1, the diaphragm 31 is used as a seal in a piston-cylinderarrangement. The outer periphery 32 of the diaphragm 31 is clampedsecurely in a groove 33 between two parts 34 and 35 of a cylinder 36 anddivides the cylinder 36 into a loading chamber 37 and a piston chamber38.

My invention uses a gas-transfer agent 40 to vary the pressure in theloading chamber 37 in accordance with the temperature of thegas-transfer agent 40. As the pressure in the loading chamber 37 isincreased, a loose-fitting piston 41 on the opposite side of thediaphragm 31 moves out, causing the diaphragm 31 to roll off the pistonside wall 42 and onto the side wall 43 of the cylinder 36, with a smoothand continuous action. Thus it moves the piston 41 and its stem 44outwardly. If the pressure is released in the loading chamber 37, aspring 45 moves the piston 41 inwardly, which, in turn, causes thediaphragm 31 to roll off the cylinder side wall 43 onto the piston sidewall 42.

The change in volume A, as discussed in the preceding section, may referto the loading chamber 37. Then the volume change takes placeunilaterally, i.e., the motion of the piston 41. Under these conditions,the length of stroke of the piston 41 may be calculated from therelation:

(Equation 5) where L is the length of stroke, A is the effective area ofpiston or bellows in cm. and AV is as in Equation 3. Heat may be appliedto the. gas-transfer agent 40 by a filament 46, which is connected to abattery 47, through a potentiometer 48. The temperature of thegas-transfer agent may be varied as desired by the potentiometer 48. Asthe temperature of the gas-transfer agent 4t) is raised, the releasedgas therefrom raises the internal pressure in the loading chamber 37,and thus the piston 41 is extended against the pressure exerted by thespring 45. As a result, the the piston 41 is moved to the FIG. 2position. (As was stated previously and will be shown later, degassingof the gas-transfer agent 40 may be accomplished by any source of heat.Thus the filamentbattery-potentiometer circuit is only one of severalpossible heat sources.)

When the temperature of the gas-transfer agent 40 is lowered by thepotentiometer 48, the internal pressure in the loading chamber 37decreases, due to ingassing, and the spring 45 returns the piston 41 toits contracted position of FIG. 1. The piston 41 may be connected by itsstem 44 to a device 49 to be actuated, and the stroke of the piston 41constitutes the actuator stroke. It is possible, by suitable choice ofparameters, to actuate through a wide range of pressures, as can be seenby referring to Table V above.

It can be seen that this device presents a very compact andself-contained actuator unit and can therefore be made small and lightin weight.

EXAMPLE 1 In an example of actual operation, the device 49 to beactuated required a pressure of at least 2.5 atmospheres and a stroke of6 cm. for its motion. Suppose the maximum pressure exerted by the spring45 against the piston 41 is 2.6 atmospheres. Then 2.6+2.5=5.1atmospheres of internal pressure to be developed in the loading chamber37.

Where the efiective area of the piston, A is 5 cm. the change of volumerequired is:

V =50 cc.=initial volume of loading chamber, and T=200 C.

Also suppose that vanadium hydride is employed as the gas-transfer agent40. From Table V under these conditions, it is found that Hence, byinserting 1.75 cc. of fully ingassed vanadium hydride into the loadingchamber 37 of the unit 34 having the above dimensions, and by heatingthe hydride 49 to 200 C., the desired effect will be achieved. Notethat, since the reaction is perfectly reversible, the piston 41 willreturn to its original position if the temperature is reduced to thevalue corresponding to P=2.5 atmospheres.

THE DUAL-UNIT ACTUATOR 5% OF FIG. 3

A dual-unit reciprocator actuating device 56 is shown in FIG. 3. Adouble-ended piston 51, comprising piston heads 52 and 53 connected by astem 54, is fitted on each end with a diaphragm 55, 55, each like thediaphragm 31 of FIGS. 1 and 2, and defining loading chambers 57 and 58,respectively, in cylinders 60 and 61. Each loading chamber 57 and S8 isprovided with a suitable gastransfer agent 62, 63, such as a Group Bhydride, whose temperature is controlled by an electrical circuit. Forthis purpose, filaments 64 and 65 may be connected to a battery 66through a disconnect switch 67, a potentiometer 68, and acurrent-limiting resistor 69.

The circuit is arranged as a voltage-divider network, so that, as thepotentiometer 68 is varied, the temperature of one gas-transfer agentwill increase while that of the other gas-transfer agent Will decrease.Hence, by employing suitable amounts of Group B hydrides as gas transferagents, a pressure dilferential may be applied to the double-endedpiston 51 by virtue of the pressure difference in the loading chambers57 and 58. Thus the piston 51 will seek a position such that equalforces are exerted on it at both ends 52 and 53. This position iscontrolled by the setting of the potentiometer 68 and thus theequilibrium position of the piston 51 may be said to follow thepotentiometer 68. The device 49 to be actuated is connected to thecenter of the piston stem 54, and its position is controllable by thepotentiometer setting.

It can be seen that'the actuator 50 eliminates the need for the returnspring 45 of the actuator 30. Furthermore, the piston 51 may be made toexecute reciprocal motion either by alternating the potentiometersetting or by controlling the setting by means of a suitable mechanicaldevice. Or, as will be seen later, the temperatures of the gas-transferagent may be controlled independently by such means as high frequencygenerators. My invention employed in this manner is capable of a widevariety of applications and has the advantage over conventional systemsthat almost an infinite number of operatingpressures and temperaturesare available. For instance, I have presented herewith a positioningcontrol that could be applied to almost any of the countless positioningapplications in industry, especially the aircraft industry for suchtasks as rudder and flap control, windshield wiper control, etc.

EXAMPLE 2 As a specific example of the use of the actuator 50,

equal amounts of titanium hydride are employed as the gas-transferagents 62 and 63. The conditions for a certain size of unit require apressure of 204 atmospheres P=204 atm. T=1000 C. A =6 CID-2 Referring toTable V, it may be seen that, under these conditions, for one loadingchamber:

30 L -5 cm.

Thus by producing a temperature of 1000 C. in one of the gas-transferagents 62 or 63, say the agent 62 in the loading chamber 57, an internalpressure of 204 atm. would be developed, and the piston 51 would move tothe right a distance of 5 cm. A possible limitation on this stroke wouldbe due to the pressure developed in the loading chamber 58 uponcompression, but this back pressure is not greater than 6 atm. if thetemperature of the gas-transfer agent 63 is no higher than 20 C. duringthe compression stroke. Thus the length of stroke will be 5 cm. If thepotentiometer setting is changed so that a temperature of 1000 C. isapplied to the gas-transfer agent 63 in the loading chamber 58 while thegas-transfer agent 62 in the chamber 57 cools, the piston 51 will thenmove to the left toward the loading chamber 57 a total distance of 10cm., since it will move cm. to recover its initial equilibrium positionand then an additional 5 cm. because of the pressure effects in thechamber 58. Hence the total length of stroke is cm. and exerts apressure of 204 atm. The cycle may, of course, be repeated by reversingthe temperatures of the gas-transfer agents again. The action describedhas been one of reciprocal motion; however, if the potentiometer 68 isleft at any of the intermediate settings, so as to produce desiredtemperatures at each source element, the device may behave as asingle-position control. Of course, a continuous range of pressure maybe obtained simply by suitable choice of container dimensions and sourceelements.

THE SINGLE-TYPE ACTUATOR 70 OF FIGS. 4 AND 5 FIGS. 4 and 5 show asingle-type actuator 70 of the same general structure as the actuator ofFIG. 1, with identical reference numerals used for identical parts. Thediiference is that, in FIGS. 4 and 5, the heating circuit contains anoff-on switch comprising a sliding contact 71 and a stationary contact72. A current-limiting resistor 73 is also used, so that externalcontrol of the battery current is unnecessary. Suppose, forillustration, that when the piston 41 is in the fully contractedposition, the sliding contact 71 which is fastened to the piston stem 44completes the battery circuit through the fixed contact 72.

Then, by virtue of the heating effect on the gas-transfer agent 40,gaseous emission occurs, and the piston 41 moves against the force ofspring 45. If the temperature and the gas-transfer agent are chosenproperly, the iston 41 will continue to extend until the contact 71slides off the fixed contact 72, thus interrupting the circuit. Thetemperature of the gas-transfer agent 40 will then drop, and thus theagent 40 will ingas, and a consequent reduction in internal pressurewill occur. Hence the spring will return the piston 41 to its contractedposition. When this occurs, .the sliding contact 71 again contacts thefixed contact 72, thus completing the heating circuit; so thetemperature of the gas-transfer agent 40 will again rise, and the cyclewill be repeated. Therefore, a reciprocating motion will occur, and thismotion does not depend upon external control.

EXAMPLE 3 It may be seen from Table V that, by employing vanadiumhydride as the source element, the equation for -AV is: I

AV=O.89V 0.88V

Suppose V 1000 cc. V =1000 cc.

Then AV=O.89 10000.88 1000=10 cc. find that and we Thus a stroke of 2cm. is obtained when operating in these lower temperature ranges. One ofthe advantages of my invention, as illustrated in this example, is theextreme simplicity of the control circuits necessary for its operation.Obviously great economy, simplicity and lightness of Weight, as comparedto conventional systems, may be achieve-d by using my invention.

THE ACTUATOR 80 USED TO OPERATE A WlNDSHIELD WIPER (FIG. 6)

A modified dual-unit reciprocator-type actuator 80 can operate awindshield wiper 81, as shown in FIG. 6. Here the actuator 80 is similarto that shown in FIG. 3, and identical numbers are used for identicalparts. The actuator 80 is connected to windshield-wiper arms 82, 83through a drive mechanism 84. The difference between the actuator shownin FIG. 3 and the actuator of FIG. 6 is that, while in FIG. 3 thetemperatures of the gas-transfer agents 62 and 63 are controlled by thesetting of the potentiometer 68, the temperatures of the gas-transferagents 62, 63 in FIG. 6 are controlled by means of double-pole,double-throw pressure switches 85 and 86, which include apressure-sensitive member 87 mounted in each loading chamber 57, 58.

In FIG. 6, suppose the double-ended piston 51 is originally in theposition shown, that is, contracted in the cylinder 60 and extended fromthe cylinder 61. When an initiating push-button switch 90 is depressed,current from the battery 66 can flow through line 91, normally closedswitch pole 92 of the switch 86, and line 93 to the filament 64', andthence return to the battery 66 via lines 94 and 95, switch 90, andlines 96 and 97. Thus, the temperature of the gas-transfer agent 62 israised, and the resultant gaseous emission in loading chamber 57 movesthe piston 51 to the right and compresses the gas in the loading chamber58 of the cylinder 61.

When the pressure in the'loading chamber 58 is raised to a sufiicientvalue, the pressure switch 86 is activated, closing a switch arm 98 andopening the switch arm 92. When the switch 93 is opened, the circuit tothe filament 64 is broken and the gas-transfer agent 62 begins to cool,with consequent decrease of pressure in the loading chamber 57. Sincethe switch arm 98 is closed, the current may now flow from the battery66 through the line 99, and switch 98, and line 100 to the filament 65,and thence via line 101, normally closed switch element 102 of theswitch 85, and line 103, to the battery 66. Since the gas-transfer agent62 is cooling and ingassing, while the temperature of the gas-transferagent 63 is rising, the piston 51 moves to the left.

When the gas in the chamber 57 is compressed to a certain pressure, theswitch 85 is activated, thus closing a switch arm 104 and opening theswitch element 102. Meanwhile, the decrease of pressure in the chamber58 causes the switch 86 to open, thus closing the switch element 92 andopening the switch element 98, and therefore preventing current flow tothe filament 65. Now the current flows from the battery 66 through theline 91, switch 92, and line 93 to the filament 64, then back to thebattery 66 through the line 94, line 105, switch 104, and lines 106 and97; so the switch 90 can be released once the cycle has been started;e.g., when the switch 86 is first thrown.

Thus the piston 51 is in position to begin a new cycle, While now it isunnecessary to depress the push-button switch 90; hence, a reciprocalaction of the piston 51 is obtained. The piston 51 is connected to thewindshieldwiper mechanism 81 through a control arm 84. The wiper arms 82and 83 are pivoted about fixed points 107 and 108, while the control arm84 has pins 110 and 111 engaging slots 112 and 113 in the lower ends ofthe wiper arms 82, 83. The control arm 84 follows the reciprocatingmotion of the piston 51 and hence drives the wiper blades 82, 83 backand forth across a wiping are 114, 115.

.13 EXAMPLE 4 As an example of operation of the actuator S0, suppose therequirements for actuation are a loading-chamber pressure of 5.1atmospheres at a source temperature of 200 C. The initial conditions areP =1 atm.; T =20 C. The electrical circuit parameters are chosen sothat, when current is applied to either of the gas-transfer agents 62 or63, their temperature will be 200 C. Assume equal amounts of vanadiumhydride are used as the gas-transfer agents. Pressure switches 85 and 86are identical and cut in at 5.2 atm., cut out at 5.0 atm. Then for oneloading chamber:

V =2.69 V =71.4 cc. P =l atm. T =20 C. P=5.1 atm. T=200 C.

It may be seen from Table V that, under these conditions:

50 L cm.

Thus the piston 51 will extend 5 cm. from each side of its equilibriumposition, and the total length of stroke will be cm.

OTHER HEAT SOURCES MAY BE USED (FIGS. 7l0) Heat may be applied to thegas-transfer agent in many different ways. In the previous examples, aDC. source of heat was employed merely for illustrative purposes.Actually, as formerly stated, any source of heat may be used. Thefollowing examples are intended to provide illustrations of a few of themany other sources of heat which may be used.

In FIG. 7 a gas-transfer agent 120 in a cylinder 121 is heated by an AC.current generator 122, applied to a filament 123, which is embedded inthe agent 120.

In FIG. 8, a gas-transfer agent 125 in a cylinder 126 is heated by aninductive heating circuit consisting of a high frequency generator 127applied to an inductive heating coil 128 which is either embedded in orsurrounds the gas-transfer agent 125.

In FIG. 9, a gas-transfer agent 130 is heated by a flame 131 that warmsthe heat-conducting walls 132 of the cylinder head 133.

In FIG. 10, a gas-transfer agent 134 is heated by a solar concentratorconsisting of a lens 135 which serves to focus rays from the sun upon areflector 136. Lenses 137 and 13S serve to direct the rays from thereflector 136 to the gas-transfer agent 134 to the heat-conductingcylinder walls 139. This device serves to increase the energy density incertain desired areas, i.e., at the agent 134.

Although the gas-transfer agent may be heated by a filament in directcontact with the hydride, it may be desirable to heat the hydrideindirectly, in one of the manners presented later.

AN ACTUATOR WITH ,CANTlLEVER-TYPE BELLOWS (FIGS. 11 AND 12) Anotheractuator 150 of variable dimensions, suitable for the employ of myinvention and depicted in FIGS. 11 and 12, employs what is called acantilever-type bellows 151. The bellows 151 comprises several flatannular sheets 152 of suitable refractory material or fabric which arejoined alternately on their outer periphery 153 and inner periphery 154,thus forming the flexible bellows. The bellows 151 can be sealed at bothends by end members 155, 156. The end member 156 may be stationary whileat the other end the member 155 is free to move and may contact themember to be actuated (not shown) when the pressure inside loadingchamber 158 is increased by heating a gas-transfer agent 160 of theunit, as by a filament 161, battery 162, leads 163, and potentiometer164. When the internal pressure in the chamber 158 is increased, thebellows 151 expands to an equilibrium position (FIG. 12). When theinternal pressure is released, the bellows 151 will contract (FIG. 11).

EXAMPLE 5 By employing titanium hydride as the source element, it may beseen by referring to Table V that and L 25 cm.

Thus a stroke of 25 cm. is obtained with a pressure of 2500 atm. andtemperature of 2000 C. These figures are formidable when contrasted withactual operating conditions of conventional systems. At the same time,the construction demonstrates the extreme simplicity of design involved.

It is worth while to mention here that the hydrides of Group B have theadvantage over conventional fuels and fluids that, at ordinarytemperatures, they are relatively stable, resulting in a consequent easeof handling and elimination of fire hazard, as long as oxygen does notcome in contact with the system.

APPLICATION OF THE ACTUATOR (FIGS. 13-14) The actuator 150 may be usedas a shock absorber or stiffness control, whose damping factor isexternally variable.

In FIGS. 13 and 14, the cantilever-type bellows 151 is shown attached byits mounting plate 157 to a frame or support 165. The other end 156 ofthe bellows 151 is attached to an axle 167, or any object capable ofimparting an upward impulse to the bellows 151, through a support plate168. A suitable gas-transfer agent is mounted in the loading chamber158, with the spiral filament 161 embedded within the gas-transfer agent160.

(The gas-transfer agent 160 and plate 157 are in the other I end of thebellows 151 from that in FIGS. 11 and 12.) v

A free end of the filament 161 terminates at a spring contact inside theloading chamber 158. The other end of the filament 161 is brought outthrough the support plate 168 and a flexible conductor 163 leads to thebattery 162. The other side of the battery 162 is connected to therheostat 164 and thence continues through the backing plate 157 to theloading chamber 158, where the conductor terminates in a contact 171.Normally, the contacts 170 and 171 (as shown in FIG. 14) do not touch,but they are arranged in such a manner that, when the bellows 151 iscompressed a specified amount, the contacts 170 and 171 will touch so asto complete the electrical circuit.

With the normal position of contacts 170 and 171 such that theelectrical circuit is not completed, assume that an impulse is impartedto the axle 167 in such a direction as to compress the bellows 151. Thecontacts 170 and 171 will then meet,'depending upon the particulardimensions involved, and thereby complete the battery circuit. Theresulting How of current through the filament 161 heats the gas-transferagent 160, and outgassing occurs with a consequent increase of pressurein the loading chamber 158. If this pressure is sufficient to overcomethe impulse, the bellows 151 will expand and thus tend to damp theimpulse. The expansion will continue until the circuit is broken by thecontacts 170 and 171 moving apart. Since the damping will be somefunction of the internal pressure in the loading chamber 158, and thusof the source temperature, the damping is controllable by the rheostat164 because it controls the temperature of the gas-transfer agent 160.Hence, the rheostat 164 may be designated the damping control.

This system of shock control offers many advantages over conventionalsystems, particularly in regard to bulk and cost. The employ of myinvention in this connection again demonstrates the extreme simplicityof its operation and use. Present day air-shock control systems aregenerally bulky and usually require an external supply of gas to alterthe internal chamber pressure as well as requiring various flow andcheck valves, etc. This, of course, may be dispensed with in my design,with resultant economy. One of the primary factors in withholdingair-shock control suspensions from use in the passenger car industry isthe expense involved. The present invention make it inexpensive enoughfor use on passengercars. Some other advantages are that it keeps anauto level despite road and load conditions, and prevents nose dive whencoming to sudden stops.

Similar results may be obtained by mounting the material 160 on thefixed member (e.g., the end 157 and there would then be less weight onthe movable portion of the system.

EXAMPLE then from Table V it may be seen AV:1.1lV O.98V =lO498=6 cc.

Thus, if

A l cm. then by Formula 5 =fi=6 cm.

and the desired result has been achieved.

If the extension desired is less than 6 cm., then all that need be doneis to lower the operating temperature by means of the damping control164.

ALTERNATE METHOD OF OPERATING CANTI- LEVER BELLOWS 151 (FIGS. 15-16)FIGURES 15 and 16 show one of the many alternative methods of varyingthe electrical circuit of FIGS. 13 and 14. In FIGS. 15 and 16 thecircuit is identical with that of FIGS. 13 and 14, except'that theelectrode 170 of FIG. 14 is replaced by an electrode 175 which isconstructed in the form of a resistance. When contact between theelectrodes 171 and 175 is made, the series resistance of the circuitwill be altered, since the electrode 171 slides on the electrode 175,which presents variable resistance to the circuit. Hence, as theelectrodes 171 and 175 move 910 a together, more current will be passedthrough the coil 161, causing a larger gas emission from thegas-transfer agent 160, which results in a larger pressure in thechamber 158 and consequently tends to expand the bellows 151. Withappropriate resistance chosen for the electrode 175, a wide range ofcurrent through the coil 161 may be chosen. One advantage of theconstruction of FIGS. 15 and 16 is that it incorporates its own ridecontrol in the form of the electrode resistance; that is, the more thebellows 151 is compressed, the greater will be the resultant pressurewithin the chamber 158 tending to oppose the cause of the motion.

A MODIFIED ACTUATOR 200 (FIG. 17)

FIG. 17 illustrates a simple diaphragm-type actuator 200 which utilizesthe principles of this invention In FIG. 17, a non-porous flexiblediaphragm 201, such as phosphor bronze (only a portion of which isshown), is secured to a non-porous support structure 202 which containsa well 203 wherein particles of a suitable gastransfer agent 204, suchas titanium hydride, are inserted along with a heating coil 205, whoseleads 206, 207 are brought outside of the well-container 203 toterminals 208 and 209 where a suitable source of electrical power is tobe connected. The well 203 of the support structure 202 is then coveredby a thin, porous membrane 210, such as porous ceramic, which serves tokeep the gas-transfer agent 204 within the well 203 but yet allowsgaseous emission from the agent 204 to escape from the well 203 into thediaphragm chamber 211.

In operation, the gas-transfer agent 204 is heated by the rise intemperature of the heating coil 205 due to the current flowing throughit from the terminals 208 and 209. The temperature of the gas-transferagent 204 may thus be varied by varying the current. Since the amount ofgaseous emission from the gas-transfer agent 204 is a function of itstemperature, the resultant gas pressure in the region 211 due to the gaspassing through porous membrane 210 is also a function of the current.Thus the pressure in the region 211 may be altered by the simpleexpedient of variation of the current connected to the terminals 208,209. As a result, the diaphragm 201 will flex back and forth, dependingupon the variation of current through the coil 205. When the currentflow ceases, the diaphragm 201 will return to its normal position, dueto the resultant ingassing of the gas-transfer agent 204.

A FLAME-OUT CONTROL ACTUATOR (FIG. 18)

FIG. 18 shows a device 220 useful for preventing gas fiow into regionswhere it would be unsafe or where it is undesirable. This device 220,which may be called a flame-out control, is essentially agetter-operated valve. It comprises a main body 221' through which gasmay flow from an inlet 222 through a valve opening 223 to an outlet 224.A pipe 225 is connected to the outlet 224 and terminates in a burnerassembly 226. Gas is prevented from flowing to the burner 226 when thevalve opening 223 is closed by a valve-closure member 227 engaging anannular valve seat 228.

The valve 227 is actuated by a bellows 230, which may be of thecantilever type, sealed at one end 231, which abuts against One endof avalve stem 232. A valve 227 is permanently secured to the other end ofthe stem 232. A port 233 at the other end of the bellows 230 is attachedto a non-porous tube 234, so that the interior of the bellows 230 andthe interior of the tube 234 enjoy a common atmosphere. The tube 234 maybe brought out of the main body 221 through nuts 235 and 236, as shown,which facilitate the easy removal and/or replacement of the tube 234 andbellows 230, as will be explained later. Seals 244 and 245 prevent gasleakage past nuts 235 and 236. The other end of the tube 234 isconnected by a non-porous flexible portion 237 to a vial 238, which maybe of non-porous ceramic, inside of which is placed a gastransfer agent240. The agent 240 is preferably fully ingassed heat-dissociablematerial in powdered form or in a filamentary form. For example, theagent 240 may 17 be powdered titanium hydride or titanium-hydride wirefully ingassed with hydrogen.

The actuator thus comprises the bellows 230, tube 234 with its flexibletubing 237, ceramic vial 238, and heatdissociable material 240 and maybe assembled as a unit at the factory prior to installation in the mainbody 221. The entire interior region of the actuator is evacuated of allgases except what is contained within the fully ingassedheat-dissociable material 240. To install the actuator assembly into thebody 221, the nuts 235 and 236 are removed and the vial 238 and tube 234are inserted through the nuts 235, 236; then the nuts 235, 236 arereinserted into the main body 221 and tightened to seal the actuatorinto the body 221. Preferably, the valve closure member 227 isspring-loaded by means of a spring 241, and a nut 242 is provided tofacilitate removal or replacement of the valve and stem 227, 232 and thespring 241, as Well as adjustment of the spring 241. A seal 246 preventsgas flow past the nut 242.

The valve 227 is actuated as follows: Heat applied to the ceramic vial238 penetrates to the heat dissociable material 240 and causes gaseousemission. Since the gas is confined to the interior region of theactuator, its internal pressure rises, and the bellows 230 expands,forcing the valve closure member 227 away from the scat, against theresistive force of the spring 241. Gas can then flow from the inlet 222to the burner 226 through the opening 223. If the heat initially appliedto the ceramic tube 238 is from a flame, such as that produced by alighted match, then the gas which subsequently emerges from the burner226 will be ignited, producing a flame 243 which envelops the ceramicvial 238. The valve opening 223 will remain open as long as the flame243 continues to heat the ceramic vial 238, so that gas will flow fromthe inlet 222 to the burner 226 all this time. If, however, the flame243 should be extinguished, accidentally or otherwise, theheat-dissociable material 240 will cool, and as a result will ingas andreduce the internal pressure of the actuator, so that the spring 241 canthen push the valve 227 against the seat 223, thereby preventing gasflow to the burner 226. Thus the mechanism can function as an automaticgas shut-off control, which prevents the serious hazard which would begenerated by unmonitored or free gas flow through the burner 226. Ofcourse, the flame 243 may be used for various purposes in addition toacting on the vial 238. It may be a pilot burner, for example, in afurnace or hot water heater, or it may b the main flame of a burner.

If desired, a non-porous glass vial may be used in lieu of ceramic vial238. Many other alternative methods of constructing this device willsuggest themselves, without departing from the spirit and scope of theinvention.

In FIGS. 1-16, 18, and 19, the diaphragm-type actuators andcantilever-type bellows actuators are interchangeable, though for aparticular application one may be far preferable to the other.

PISTON-DRIVING ACTUATOR (FIGS. 19 and 20) FIG. 19 illustrates anotherhighly useful application of my invention. In this instance, an actuator250 drives a piston 251. A non-porous cylinder 252, preferably metal, isprovided with a loose-fitting piston 251 connected to a crankshaft 253by means of a piston rod 254 and crankpin 2.55. A flywheel 256 isprovided on one end of the crankshaft 254. The piston 251 is in contactat its upper end with a non-porous flexible diaphragm 257 of the typeshown in FIGS. 1 and 2. The rim 258 of the diaphragm 257 is sealed tothe top 259 of the cylinder 252 by a non-porous cap 260. Directlyunderneath the cap 26) is secured a porous container 261, which may beporous ceramic. A heating coil 262 and a suitable amount of agas-transfer agent 263 (for example, fully ingassed titanium-hydride) isplaced inside of the container 261, and the leads 264, 265 for the coil262 are brought out of the cap 269 through hermetic seals 266 and 267and terminate at contacts 268 and 269, across which an alternatingcurrent E.M.F. 270 is placed. The porosity of the container 261 keepsthe particles of the gas-transfer agent 263 from escaping, but willpermit gas to flow freely through it. A rectifier 271 may be provided inthe lead 264.

In operation, the alternating current 270 may have a wave form like thatshown in FIG. 20. Assume, for example, that positive-voltage portions272 of the current are passed by the rectifier 271, while the negativeones, 273, are prevented from flowing. When the first positive portion272 of the current passes through the heating coil 262, the temperatureof the gas-transfer agent 263 is elevated. As a result, gas is releasedfrom the agent 263 and passes through the porous container 261 into aloading chamber 275 of the cylinder 252. The internal pressure in thischamber 275 causes the diaphragm 257 to expand against the piston'251and forces the piston 251 away from the container 261. The resultingmovement of the piston 251 causes a rotary motion of the crankshaft 253.

When the current reverses, a negative pulse 273 is sent to the terminal268 but is prevented from passing through the heater coil 262 by therectifier 271; therefore, the gas-transfer agent 263 cools during thisportion of the cycle. Meanwhile, the inertia of the flywheel 256 carriesthe piston 251 back up to the top of cylinder 252, while thegas-transfer agent 263 is cooling and therefore ingassing; so thepressure in the chamber 275 is reduced. This reduction in pressure helpsto draw the piston 251 to the top of the cylinder 252.

With proper synchronization, when the piston 251 has reached the top ofthe cylinder 252, the gas-transfer agent 263 has been reingassed. Atthis point the current again reverses and sends a positive pulse 272through the heater coil 262, resulting in repetition of the cyclepreviously described. Thus, continuous motion of the crankshaft 253 isobtained merely by applying suitable alternating current 270 at theterminals 268 and 269.

Although only one piston actuator 250 has been drawn, the method canobviously be extended to two or more piston actuators connected to thesame or different crankshafts. The piston actuator. 250 indicates in astriking manner. the simplicity and practicality of this invention. Thisunit is entirely self-contained and operates without 'valves of anykind. The only external requirement is a suitable source of current 270.

The method of retaining the gas-transfer agent 263 inside of the porouscontainer 261 is equally applicable to the constructions of FIGS. 1through 16, where, in the description of these previous figures, noprecise structure for holding the gas-transfer agents was described.

EXAMPLE 7.USE on GROUP A HYDRIDE IN THE ACTUATOR In connection with theactuator of FIGS. 11 and 12, a Group A hydride, such as copper hydride,may be employed as the gas-transfer agent 160. Since the solution ofhydrogen in Group A materials is an endothermic reaction, hydrogen willbe liberated as the temperature of the hydride is lowered, consequentlythe bellows 151 will expand to the position shown in FIG. 12 whencurrent through the filament 161 is reduced. The bellows 151 willcontract when this current is increased. In certain types of conditionsthis reversed type of operation may present advantages.

EFFECT OF OUTGASSING ON ELECTRICAL PROPERTIES OF THE HYDRIDE For manyapplications it will be satisfactory for the hyrdide to be in directcontact with the filament, especially when low filament voltages andtemperatures are employed. However, at high voltages and/ ortemperatures, shorts across the filament may occur. This is a result ofa property of hydrides in general, namely, a change in electricalresistance when the gas'content changes. For example, the resistance oftitanium or zirconium hydride decreases as their hydrogen contentdecreases, so that filament temperatures that cause the hydride tooutgas also lower its resistance to the point where an additionalincrease in current due to lowered resistance may generate undesiredheat and cause serious electrical or mechanical leaking or maypermanently damage or alter the operating characteristics of the system.Lowering pressures (at a given temperature) also result in outgassingthe hydride and changing its resistance.

Several solutions to this problem follow.

INTIMATELY MIXING THE HYDRIDE WITH AN INSULATOR One way of solving theproblem just stated is to electrically insulate the hydride particles atall times, with out inhibiting the passage of gas to or from thehydride. A unique way of accomplishing this is to intimately mix thehydride with a powdered insulating material such as microscopic aluminaor quartz. In the construction of test units it was determined thatball-milling a mix of microscopic alumina and titanium hydride in equalparts by weight for several days produced very satisfactory results.Test assemblies employing filaments of 0.002 diameter tungsten wireembedded in this mix have periodically withstood high filament voltagesand high current (e.g., 45 volts, 4 amps, at 15 p.s.i.g., cycling fromroom temperatures to 3000" F.) for periods in excess of onehalf hourwithout mechanical or electrical failure or noticeable change inoperating characteristics.

Additional advantages derived from the use of the hydride-insulator mixare thatmuch less filament current is required to cause a given amountof gaseous emission than is necessary when unprepared hydride is used,indicating an increase in the energy transfer eificiency.

RADIANT HEATING OF THE GAS-TRANSFER AGENT In FIG. 21 a heating capsule313 is placed within a non-porous container 314 which might represent asection of cylinder 34 as shown in FIG. 1, or may be the well 203 ofFIG. '17, for example. The capsule 313 comprises a quartz or sapphiretube 315 plugged at both ends with electrically insulating and porouscaps 316 and 317, which are supported on the container 314 by means ofbrackets 318 and 319. The gas-transfer agent 320 is placed within thetube 315, and a tungsten, molybdenum, or other suitable filament 321 iswrapped around and against the periphery of the tube 315. Conductors 322and 323 pass through feed-through insulators 324 and 325 and connect tothe ends 326 and 327 of the filament 321. A suitable source of AC. orDC. current is connected to terminals 328 and 329. When current passesthrough the filament 321, energy from the hot filament is radiantlycommunicated through the walls of the tube 315 to the gas-transfer agent320, whereupon, if titanium or zirconium hydride, for example, isemployed as the gas-transfer agent, gaseous emission proceeds throughthe plugs 316 and 317 into the region R within the container 314. It isimportant that this region R does not contain oxygen or any other gaswhich might react unfavorably with either the gas-transfer agent 320 orthe filament 321. A preferable atmosphere may be, as previouslydescribed, one composed of inert gases or of gas native to the hydrideor gas-transfer agent 320.

This method of heating offers the advantage that the heating elementnever comes into direct contact with the gas-transfer agent 320 andhence is insulated at all times from the filament.

A modified apparatus for radiantly heating the gastransfer agent isshown in FIG. 22. Here a heating unit 330 is mounted to the walls of anon-porous container 331 by means of brackets 332 and 333. As in FIG.21, the

interior of the container 331 represents a portion of the region R inwhich it is desired to provide alteration of pressure. The heating unit330 comprises a porous container 334 through which passes a quartz orsapphire tube 335. The ends of the tube are brought out of the container331 through feed-through insulators 336 and 337. A filament 338 whichmay consist of tungsten or molybdenum wire or other suitable materialpasses through the center of the tube 335 and is connected to terminals339 and 340. A suitable amount of gas-transfer agent 341 is placed inthe container 334 around the tube 335. Current from an AC. or DC. sourceapplied to terminals 339 and 340 heats the filament 338 which, in turn,radiantly transfers energy through the transparent walls of the tube 335to the surrounding gas-transfer agent 341, and causes it to releasehydrogen. The porosity of the container 334 is such that thegas-transfer agent 341 will be retained in the interior of the container334, yet gas may flow freely through the container walls. Thus, thepressure in the region R of the container 331 may be altered. Here,again, the advantage of this type of construction is evident, for it isnoted that the heating filament 338 does not come into direct contactwith the gas-transfer agent 341.

Although the tube 335, shown in the interior of the container 334, hasbut one. loop, several more loops may obviously be added to the tube;for example, the tube may be formed in a spiral or helical form toprovide a greater heating area to the gas-transfer agent 341. The quartzor sapphire tube 335 may, for example, be 0.060" outside diameter and0.040 inside diameter, while the tungsten or molybdenum filament 338 maybe 0.003" or 0.004 in diameter. To prevent oxidation of the filament338, copper leads 342 and 343 may connect the ends of the filament 338to the terminals 339 and 340, and these leads 342, 343 are then sealedwhere they leave the tube 335.

HEATING THE HYDRIDE DIRECTLY In FIG. 23 a gas generating and heatingunit 345 is placed in the interior of a container, represented by thebroken line 346, and is mounted to it by means of insulated brackets 347and 348. The unit 345 comprises the gas-transfer agent 349, such astitanium hydride, for example, in filamentary form. The agent 349 iswrapped with a ribbon-like helix 350, which in this case may be madefrom molybdenum.

In the unit 345 a unique property of hydrides is employed. Theresistance of hydride materials to current is a function of the amountof gas taken up by the hydride. For example, it is known that theresistance of titanium or zirconium hydride decreases as the amount ofhydrogen content of the hydride decreases. Thus, when the hydride 347 isinitally in the ingassed state, it presents a comparatively highresistance to current flow. So, when the voltage or current source,which in this case is represented by a battery 351, is connected inparallel by leads 352 and 353 to the ribbon 350 and by leads 354 and 355to the hydride agent 349, current will initially flow primarily throughthe ribbon 350, because it initially has the lower resistance. Thiscauses the temperature of the hydride 349 to rise, and it releaseshydrogen, thereby decreasing its resistance to current flow. At the sametime, the increase in temperature of the molybdenum ribbon 350 causes anincrease in its resistance. Thus, as the temperature of the unit 345 israised, the current will have an increasing tendency to flow through thegas-transfer agent 349, in preference to the ribbon 350. Similarly, whenthe current through the ribbon 350 and the hydride 349 is reduced, thedrop in temperature allows the hydride 349 to re-ingas, resulting in ahigher resistance to current flow by the hydride 349 and a lowerresistance by the ribbon 350. It is thus possible to choose the correctamount of hydride and ribbon materials so that the current flow throughthe whole unit 345 depends linearly upon the applied voltage.

21 An advantage of the use of molybdenum as the helical ribbon 350 isthat, in case of possible welding between the molybdenum and thetitanium hydride, for example, no undesirable effects occur. That is,alloying molybdenum with titanium does not seem to adversely affect theproperties of these materials, so far as application to actuator use isconcerned. As a matter of fact, the addition of small amounts oftitanium to molybdenum increases the strength and ductility of themolybdenum. As in FIGS. 2-1 and 22, the atmosphere surrounding theelement 345 should be one that does not contain gases which will reactunfavorably with the hydride 349 or the ribbon 350.

HEATING THE GAS-TRANSFER AGENT BY ARC DISCHARGE In FIG. 24 a dischargecapsule 360 comprises a porous electrically insulating tube 361, whichmay be porous ceramic, which has at each end fiat-ended metal electrodes362 and 363, between which is located an amount of a suitablegas-transfer agent 346, such as titanium hydride, for example. Theporosity of the tube 361 assures that the gas-transfer agent 364 will beretained inside while gas may pass freely through the walls. Thiscapsule 360 is mounted by insulating brackets 365 and 366 to thecontainer represented by the dotted lines 346, in which it is desirableto alter the internal pressure. Conductors 367 and 368 are connected tothe electrodes 362 and 363 and are in series with a variable resistor369 and the secondary of a transformer 370. An alternating currentgenerator 371 is applied to primary terminals 37 and 373. As the voltageapplied is increased in magnitude, a

point is reached at which an arc discharge takes place between theelectrodes 362 and 363, resulting in a momentary surge of current whichmay be of the order of several amperes. This large magnitude of currentrapidly heats the gas-transfer agent 364 and causes gaseous emission.The gas passes through the walls of the container 361 into the interiorof the container 346 and thus alters the pressure there. The aredischarge voltage is a function of the shape of the electrodes 362 and363, which in this case are shown as flat-faced, but they may be anyother suitable shape, for example, pointed. It also is a functionsomewhat of the distance between the electrodes and of the conductivityof the gas-transfer agent 364. This allows several parameters to bechosen to accommodate a wide range of arc discharge voltages. It hasbeen explained previously that the form of the hydride introduced intothe tube 361 has a marked effect upon the electrical characteristics ofthe system. If the hydride is ball-milled with an equal part by weightof alumina, the breakdown voltage between the electrodes will be greatlyincreased over that occurring when unprepared hydride is used. In caseswhere it is desirable to produce low voltage discharges, unpreparedhydride may be used with considerable success. The voltage and currentapplied to the electrodes 362 and 363 are also variable and limited bymeans of the resistor 369.

Although the transformer 370 may be of conventional design, it may be asaturable reactor. When the secondary current of the saturable reactortransformer 370 increases to a certain magnitude, reaction takes placeto limit the secondary current to a safe level. This provides a safetyfactor.

One particular advantage of the capsule 360 is that intense heat may beapplied to the gas-transfer agent 364 over relatively short periods oftime, and rapid outgassing of the agent 364 will take place. Thispermits rapid response of an actuator which uses this type of heatingarrangement.

To those skilled in the art to which this invention relates, manychanges in construction and wide-1y differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

I claim:

1. In an actuator device, a gas-transfer capsule, comprising a generallycylindrical hollow container with electrically insulating walls,metallic hydride insaid container, and an electrical heating filamentwound around the outside of said hollow container.

2. In an actuator device, a gas-transfer capsule, comprising aporous-walled container, metallic hydride inside said container thatemits hydrogen gas when heated, an electrically insulating tube insidesaid hydride, and an electrical heating filament inside said tube andthereby insulated from said hydride.

3. In an actuator device, a gas-transfer capsule, comprising a block ofmetallic hydride which is electrically conductive and whose conductivitychanges when heated, said hydride emitting hydrogen when heated, anelectrical heating filament wound around said block, and a source ofelectric current connected across said filament and, in parallel, acrosssaid block.

4. In an actuator device, a gas-transfer capsule comprising a porous,electrically insulating tube with electrodes at opposite ends thereof,metallic hydride in said tube between said electrodes, and means tocause an arc of discharge voltage between said electrodes.

5. An actuator comprising a gas-tight bellows; a metallic hydride insaid bellows, which changes the internal pressure thereof by releasingquantities of hydrogen large in proportion to said hydride when thetemperature of said hydride is changed; and means for heating saidhydride.

6. An actuator comprising -a gas-tight bellows; a hydride of the typethat emits hydrogen when heated in said bellows; an electrical filamentin said hydride; a source of electrical power; and a circuit connectingsaid source to said filament.

7. The actuator of claim 6 wherein said filament and said hydride arelocated at one end of said bellows and said circuit includes a firstswitch element extending from said filament inside said bellows and asecond switch element inside said bellows supported by the opposite endof said bellows, for breaking said circuit when said bellows expands apredetermined amount and closing said circuit when said bellowscontracts a predetermined amount.

-8. The actuator of claim 7 wherein said first switch element comprisesa resistance element so as to increase the heat energy applied to saidfilament as said second switch element moves closer to said filament,after contact with said first switch element.

9. An actuator comprising a pair of coaxial containers each closedexcept on one end; diaphragm means for each container closing that endso as to make each said container gas-tight and enclosing therewith aloading chamber; a charge of metallic hydride in each said chamber torelease hydrogen gas upon a change in temperature in one direction andto take up gas upon a change in temperature in the opposite direction;electrical heating means for each said container for changing thetemperature of said metallic hydride; a switch in each said containerthat is closed when its diaphragm reaches an extreme position,reciprocating shaft means extending along the common axes of saidcontainers and operatively connected to both said diaphragms formovement with them; and electrical circuit means including said switchmeans for turning off the electrical heating means in one said chamberand turning on the electric-a1 heating means in the other said chambereach time a said switch means is closed at the extreme position of thediaphragm.

No references cited.

SAMUEL LEVINE, Primary Examiner.

1. IN AN ACTUATOR DEVICE, A GAS-TRANSFER CAPSULE, COMPRISING A GENERALLYCYLINDRICAL HOLLOW CONTAINER WITH ELECTRICALLY INSULATING WALLS,METALLIC HYDRIDE IN SAID CON-